Mayor Bloomberg said yesterday that he “could not support” Judge John Roberts Jr.’s nomination to the Supreme Court if the judge doesn’t clearly articulate that he supports women’s right to abortion.

“Judge Roberts is going to have an opportunity to share his judicial philosophy with us in the coming months,” Mr. Bloomberg said, standing outside Kings County Hospital yesterday afternoon. “And I tell you what I’ll be listening for – a clear indication that he accepts Roe v. Wade as the law of the land. Anything less than that – any sense that a moderate conservative voice might be replaced by something more extreme – is simply not acceptable.”

Mr. Bloomberg’s comments came as he received the endorsement of NARAL Pro-Choice New York, a group that traditionally supports Democrats. It endorsed Mark Green in the 2001 election.

NARAL’s executive director, Kelli Conlin, called Mr. Bloomberg “one of the most pro-choice mayors in America” and praised his administration’s efforts to improve women’s health care in New York City, particularly his plans to enhance abortion care and training at public hospitals and his $3 million program to reduce unintended pregnancies by promoting emergency contraception.

Mr. Bloomberg, repeatedly referring to abortion as a “basic human right,” said he was honored to receive the endorsement.

Political observers say he should be.

A veteran political consultant, Hank Sheinkopf, said: “It’s very, very, very significant for the mayor. It gives him access to a bloc of voters. … It reduces the negatives around his Republicanism.”

Mr. Bloomberg’s Democratic rivals dismissed the endorsement.

“Fernando Ferrer has a 20-year career of supporting a woman’s right to choose,” a spokeswoman for the Democratic front-runner, Christy Setzer, said. “Mike Bloomberg is trying to have it both ways. He claims to be pro-choice on one hand but then gives hundreds of thousands of dollars to anti-choice Republicans on the other hand.”

At yesterday’s event, Mr. Bloomberg said he has supported groups that advocate for abortion for years – and he defended his right to donate money to Republican candidates.

“There are pro-choice people in the Republican Party and pro-choice people in the Democratic Party,” he said. “This is not a partisan issue. This is an issue of basic human rights for women and it transcends party line, and I support elected officials who believe as I do that women have a right to choose what to do with their bodies.”

Yesterday, Mr. Ferrer’s campaign sent out a press release that quoted him as opposing Judge Roberts’s nomination. C. Virginia Fields came out against the nomination on Wednesday.